Plain bearings made using a variety of materials adapted with fillers to provide improved wear resistance and/or reduced friction characteristics are well known in the industry. These bearings may take the form of a simple cylinder, or may have a flange on one end to aid location in the housing and/or provide a thrust washer surface. Certain applications require a double flanged bearing so that the bearing is securely located in a cylindrical housing and/or to provide thrust washer surfaces at each side of the housing.
As can be appreciated, adding a flange to one or both sides of the cylindrical bearing may increase the complexity of both manufacture of the bearing and installation of the bearing.
With reference to, for example, a conventional double flange bearing, it can be appreciated the double flange bearing is more difficult to make than a simple cylinder bearing or a cylinder with a single flange bearing form. Polymer bearings can, for example, require complex and expensive multi-part tooling for the Injection Moulding Machine to produce a single part double flanged bearing, or to produce a single part bearing which can be compressed or manipulated in such a way as to pass through the housing before the second flange is formed. Other known methods of production include a design of housing which can be assembled around the double flanged bearing, or a bearing which allows assembly into the housing in multiple parts to create a double flanged bearing.
European Patent EP 1 869 334 owned by igus GmbH provides a unique double flange bearing where the second flange is formed by bending a plurality of collar elements from a flat position where the collar elements are co-planar with the cylindrical bearing to a flange position where the collar elements are perpendicular to the plane of the cylindrical bearing. The bending of the collar elements has a number of deficiencies, however. One exemplary deficiency is the bend location may cause a stress concentration or potential fracture point in the bearing. Another exemplary deficiency is the difficulty in bending the collar elements to name but two exemplary deficiencies.
Moreover, long polymeric cylindrical bearings, whether flangeless, single flange, or double flange, are difficult to make conventionally. As is generally known in the art, long polymeric molds require significant, large tooling to accommodate the length of the bearing. Additionally, the mold may require several injection gates along the tooling for the mold, making the manufacture of long cylindrical plain bearings complex. The multiple gates and long tool also may lead to problems with filling the mold. The long mold with multiple injections may result in the polymer cooling to inhibit proper knitting of the material along a joint or weld point, sometimes referred to as cold welding resulting in some weakness in the bearing material.
With the above in mind, there is need in the industry for a double, single, or non/un-flanged plain polymer bearing that may be formed using conventional injection molding techniques but not suffer the deficiencies of which a few are outlined above.